Contact element



2,4l8,ll ri 2,418,811 coNrAc'r ELEMENT Roy L. Adams and Lyall Zickrick,

Schenectady,

N. Y., assignors to General Electric Company, a corporation of New York No Drawing. Application October 8, 1943,

Serial No. 505,536 3 Claims. (Cl. 171-325) Our invention relates to contact elements and particularly to such elements as are used with electrical apparatus as current collecting brushes.

An object of our invention is to provide an improved electrical contact element.

A further object of our invention is to provide an improved electric current collector contact element including a carbonaceous material and provided with an inorganic lubricant for the contact surface thereof.

Further objects and advantages of our invention will become apparent and our invention will be better understood from the following description, and the features of novelty which characterize our invention will be pointed out in the claims annexed to and forming a part of this specification.

It has been found that under normal atmospheric conditions with average humidity atmospheric water vapor and oxygen together provide one of the best known lubricants for the contact surfaces of carbon and metal-graphite brushes and similar bearing surfaces. It also has been found that electrical contact elements made of porous blocks of finely divided electrically conductive material such as carbon or metal-graphite brushes tend to wear away very rapidly in dry or rarefied atmospheres.

We have found that a relatively movable contact element such as might be used for an electrical brush contact or a relatively movable bearing element for contact with another member, such as a rotating slip ring or commutator, will have a relatively long wearing life when it is made of a graphitic or carbonaceous material intimately combined with a metal and sulphur. Different proportions of these ingredients have been found to be useful for diiferent operating conditions in connection with such contact elements, and it has been found that a contact element made of a pressed and sintered or fired mixture of finely divided powders of graphitic material with a metal of high electrical conductivity, such as copper, or silver, and sulphur or a metallic sulphide, provides a particularly desirable combination.

We have found that this type electrical brush contact element is preferably formed of a block of carbonaceous material such as finely divided graphite, a metal such as finely divided silver, and a metallic sulphide such as silver sulphide. In some instances, the sulphide may be formed during the manufacturing process by adding powdered sulphur to a mixture of graphite and powdered metal, mixing, heating, and pressing the mixture together and thereby forming a metallic sulphide mixed with graphite and metal. In thus making a contact element, the carbonaceous material is mixed with the metallic powder and sulphur and is pressed in a mold at to 50 tons per square inch pressure and is then heated in a reducing atmosphere, such as hydrogen, at a temperature between 650 and 700 C. Another method of making this type contact element which has been found to be successful is to mix finely divided copper oxide, such as black copper oxide (CuO), with a finely divided carbonaceous material, such as graphite, to form a slurry with water, afterwhich this mixture is heated while it is being mixed until it forms a dry powder. This mixture is then heated in a reducing atmosphere at a temperature between 600 and 900 C. to reduce the copper oxide, after which this powder is mixed with a finely powdered sulphur and pressed to the desired shape at a pressure of several tons per square inch and heated for several hours at a temperature between and 200 C. It is then fired in a reducing atmosphere for about four hours at a temperature between 700 and 750 C.

While we have described particular embodiments of our invention, modifications thereof will occur to those skilled in the art, and we desire it to be understood, therefore, that our invention is not to be limited to the particular arrangements disclosed, and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical contact element including a block formed of carbonaceous material, a metal, and a sulphide of said metal.

- 2. The method of making an electrical contact element including mixing finely divided carbonaceous material with finely divided copper and copper sulphide, pressing the mixture in a mold at several tons per square inch pressure, and heating it in a reducing atmosphere at a temperature between 650 and 700 C.

3. The method of making an electrical contact element including mixing finely divided carbonaceous material with a metallic powder and a metallic sulphide, pressing the mixture in a mold at several tons per square inch pressure, and heating it in a. reducing atmosphere at a temperature between 650 and 700 C.

ROY L. ADAMS. LYALL ZICKRICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,121,960 Whitney Dec. 22, 1914 FOREIGN PATENTS Number Country Date 249,864 German Aug. 1, 1942 

